The rotating spindle of a turning machine, e.g. a lathe, can have a power-operated workpiece holder, particularly a chuck. A clamping head attached to an end of the rotating spindle between the rotating spindle and the workpiece holder has a plurality of adjustable power-operated clamping members for clamping and fixing the workpiece holder on the clamping head and also with a clamping rod for the workpiece holder located in the hollow spindle traversing the clamping head which is axially slidable between two positions corresponding to the open or closed state of the workpiece holder under power, is attached with a central clamping member of the workpiece holder and is rotatable relative to the rotating spindle at least into a position corresponding to the open state of the workpiece holder. The clamping rod is couplable and decouplable from the clamping member by rotation.
In a clamping device or chuck retainer as described in German Open Patent Application No. 33 28 291 the power-operated clamping members are radial clamping bolts guided radially in the clamping head body. Power-pistons operating these clamping members are provided in cylindrical spaces in the clamping head body. A clamping cylinder with a rotary piston is provided for rotation of the clamping bar. It is arranged with axial pistons for axial operation of the clamping bar on the rear end of the rotary spindle axially beside an additional clamping cylinder. The cylinder piston unit for each clamping piece in the clamping head body and the clamping cylinder with rotary piston for rotation of the clamping bar involve considerable construction and operating or maintenance costs.
A clamping device or chuck retainer is described in German Open Open Patent Application No. 30 45 536 in which the clamping members are guided radially in the clamping head body and are adjustable by a clamping tube with a wedge drive which is slidable axially under power operation in the rotating spindle receiving the clamping bar and is nonrotatable relative to the rotating spindle. A coupling bar is provided for coupling and decoupling the tubelike with respect to the central clamping member of the workpiece holder which is guided inside the clamping bar axially slidable under power operation. The clamping bar and the coupling bar like the clamping tube are nonrotatable relative to the rotating spindle. Disadvantageously the coupling bar and three clamping cylinders with their own clamping pistons for the clamping tube, the clamping bar and the coupling bar are all necessary. Also the clamping cylinders occupy a disadvantageously large axial structural length at the rear end of the rotating spindle.